Rails 4.2: Internal Server Error with Maximum file multiparts in content reached

Question

Just upgraded to Rails 4.2 and I get Internal Server Error on localhost and in production when trying to edit a model with multiple has_many objects. This is the message I see on the rails s console

!! Unexpected error while processing request: Too many open files - Maximum file multiparts in content reached

The request does not even get to the controller i.e., I DO NOT see the usual following lines in rails s console

Started GET "/feeds/3/edit" for 127.0.0.1 at 2015-01-04 20:07:19 -0800
Processing by FeedsController#edit as HTML
......
......

Any clues?? Using Ruby 2.1.5 upgraded to 2.2 with no luck.

Caltanissetta

Getting the same thing here, Rails 4.2.0 and Ruby 2.2.0. – Luz

Rack 1.6.4 contains a fix for this. – Gilead

Answer 1

It looks like the multipart limit was added in the Rails 4.2 version of Rack (https://github.com/rack/rack/commit/b0b5fb9467e6ed777d3eaf35afc81d758e308aab). The default is 128, which may be too little for your purposes, it was for mine. Setting the value to 0 in an initializer removes the limit and fixes the problem:

Rack::Utils.multipart_part_limit = 0

I would suggest tailoring the value until it fits your needs so your server doesn't run out of file handles. My app uses a massive form and setting it to 512 seemed to work for me.

Luz

Thank you Craig. Will test and mark your answer as accepted if it works. I do have a long form. The shorter forms work fine. – Caltanissetta

It looks to us like the patch that was introduced is counting one open file per form element, not just files. So if you have a nested form, you quickly run out of "files". Seems like a bad patch. – Vaporous

Rack 1.6.1 does NOT contain this fix. Looks like that will be in the 1.7 release instead :( – Gilead

Rack 1.6.4 contains a fix for this. – Gilead

Hey i m facing the same problem,Where i can place this line? – Rife

@JigarBhatt I place it in config.ru, for reference – Ali

Answer 2

You can also pass a Environment variable to the app, as you can see here(https://github.com/rack/rack/blob/8d21788798b521b97beb10047ebf593ddc0aaed2/lib/rack/utils.rb#L75).

RACK_MULTIPART_PART_LIMIT=0 rails server

Parturient

But you should set both RACK_MULTIPART_PART_LIMIT and RACK_MULTIPART_LIMIT because of the code remark RACK_MULTIPART_LIMIT was introduced by mistake and it will be removed in 1.7.0 – Mesial

Hey i m facing the same problem,Where i can place this line? – Rife

@JigarBhatt you can set this env variables on the line that you execute your script. For example: RACK_MULTIPART_PART_LIMIT=0 ruby app.rb or you can export you variable an then run your script. export RACK_MULTIPART_PART_LIMIT=0 then ruby app.rb – Parturient

Answer 3

It looks like there is a bug in Rack 1.6 where all HTML input elements get counted as an open file in a multipart form. As others point out, you can change the limit to 0 to disable the feature, or bump the limit.

https://github.com/rack/rack/pull/814

Gilead

This has been merged into 1.6.4 it appears – Gilead

Answer 4

In Rails > 6 you will need to use multipart_total_part_limit instead of multipart_part_limit.

Rack::Utils.multipart_total_part_limit = 0

Source

Papain